The 5AR4 Rectifier

The 5AR4. The 5AR4 is one of the most iconic rectifier tubes, with a legendary reputation for its soft start and NOS tube longevity often far beyond expectation. These are a few of the Mullard examples, with the first being the metal base made in Holland tube. This is one of the most well-known tubes of any type. Next is the saw tooth 5AR4 (labeled G.E. and RCA respectively) and finally a modern JJ made in Czech Republic. The older Mullards are hard to beat. My advice is to buy a new testing Mullard while they still exist affordably, and never need that tube again. It may last 10's of thousands of hours, which is a lot, and they sound best. This is an easy win. Spec sheets for the 5AR4 can be found here: here.

The 5AR4. The metal collared Mullard 5AR4 are the most desirable and the most expensive of the tube type, but they reportedly last for many tens of thousands of hours, so in the long run it might be worth the expense. The "saw-tooth" Mullard is a classic tube and is a great place to be in 5AR4. Both of these sound a lot better than any of the new 5AR4 rectifiers I have experience with. Be warned that like most of the European tubes, the chalky white labels on these tubes are very easy to rub off, it takes hardly a brush of the fingers, which makes this particular metal collared 5AR4 all the more rare.

The 5AR4. Mullard-made 5AR4 for GE and RCA respectively. These tubes were often found in tube receivers for Scott, Fisher, Eico, etc.